Labour MP Tāmati Coffey using his personal experience to fight for change in surrogacy laws

Labour MP Tāmati Coffey is fighting to change surrogacy laws after he and his partner formally adopted their biological son.

Mr Coffey and partner Tim Smith welcomed baby Tūtānekai in July, but the couple couldn't legally claim him as theirs until an adoption process was carried out with the surrogate.

The couple finally officially finished the process yesterday. Today, Mr Coffey officially lodged a Member's Bill aiming to update the rules around surrogacy.

"It was shaped by personal experience," he told 1 NEWS.

"We still underly [the adoption joy] with the fact we resented having to adopt our own biological son, but that's the process as it stands now and hopefully there will be some law changes to make sure that we modernise things so that couples aren't having to go through what we went through."

The 'Improving Arrangements For Surrogacy Bill' includes amendments to five Acts and two sets of Regulations.

They're all issues Mr Coffey says he and his partner came across.

"These are all things that we've experienced and we've lived through, and now that we're over the line we're looking back and seeing how we can make things better for other surrogates coming through."

Professionals told them the surrogacy laws were "completely outdated" and Mr Coffey says he wants to modernise them.

"We decided to embark on our fatherhood journey… and realised [the laws] weren't actually fit for purpose."

Under current New Zealand law, at the time of birth the child's legal parents are the surrogate mother and partner.

As part of the formal adoption process, the surrogate needs to confirm she doesn't want to keep the baby and the biological father needs to apply to adopt.

Under Mr Coffey's proposed bill, that would change and the intending parents would get automatic legal status once gaining custody of the child.

"It also enforces the legal obligations of intending parents if they refuse to take custody by making them liable for child support, even if they do not have custody of the child," the bill states.

Another proposed change would be the creation of a register to make it easier to find surrogates and donors, and changing birth certificates to allow more contributors.

"We think in line with the UN conventions on the rights of the child, which is the right to know about your genetic whakapapa, that it's right we adapt our birth certificates to make them fit for purpose as well," Mr Coffey says.

It's not just a "rainbow issue" but it could be a win for all New Zealanders.

"We think it's the right of every New Zealander to have a family and to be acknowledged as the parent of their child. At the moment our laws… prevent that from happening," he says.

"This is about all Kiwi couples that want to start their own family. This isn't just a gay issue, this is about all couples that want to go through surrogacy and can look forward to a more streamlined process."

He also wants to change the rules around financial contributions towards the expenses surrogates face - such as helping contribute to living expenses with their surrogate who couldn't work in her final week of pregnancy.

While the bill is in Mr Coffey's name, he says a lot of work was also done by fellow Labour MP Louisa Wall.

The proposed bill will need to be drawn in a ballot before being debated in Parliament.

Discussions are also underway with Justice Minister Andrew Little as to how else changes could be brought in, Mr Coffey said.